Feed control apparatus for a rotary tool

ABSTRACT

A saw blade is rotated by an electric motor while fed by a hydraulic feeding motor into a workpiece. A regulating throttle controls the hydraulic motor to vary the feeding speed, and is operated by a control means to either slowly increase the feeding speed or to rapidly reduce speed in accordance with the indications of a torque responsive amperemeter in the circuit of the electric motor. Two manually settable stops limit the movement of the regulating throttle independently of the control means and of the indication of the amperemeter in two end positions in which the hydraulic feeding motor is set to a maximum and a minimum feeding speed, respectively, selected for a specific workpiece.

Kaltenbach 1451 Feb. 13, 1973 54] FEED CONTROL APPARATUS FOR A 2,989,6746/1961 Hawkins et al. ..83/72 UX ROTARY TOOL 3,545,310 12/1970 Porath etal. ..40s/11 Inventor: Dieter Kaltenhach, Rebweg 33,

7850 Lorrach, Germany Filed: Sept. 15, 1971 Appl. No.: 180,654

Field of Search ..83/72, 74, 75, 62, 470, 490, 83/522, 554; 408/10, 11

References Cited UNITED STATES PATENTS Sykes ,.s3/72 Remmen ..83/72Primary EXaminer--Frank T. Yost Att0meyMichael S. Striker [57] ABSTRACTA saw blade is rotated by an electric motor while fed by a hydraulicfeeding motor into a workpiece. A regulating throttle controls thehydraulic motor to vary the feeding speed, and is operated by a controlmeans to either slowly increase the feeding speed or to rapidly reducespeed in accordance with the indications of a torque responsiveamperemeter in the circuit of the electric motor. Two manually settablestops limit the movement of the regulating throttle independently of thecontrol means and of the indication of the amperemeter in two endpositions in which the hydraulic feeding motor is set to a maximum and aminimum feeding speed, respectively, selected for a specific workpiece.

10 Claims, 7 Drawing Figures PAIENTEDFEBISIQIS 3,715,946

SHEET 1!]? 5 PATENTEDFEB 13 ms 3. 715.946 SHEET 2 OF 5 F lg. 2

PATENTEU FEB 1 3 ms SHEET 4 OF 5 vm mm PATENTEDFEB13 197s SHEET 5 BF 5LY MQ FEED CONTROL APPARATUS FOR A ROTARY TOOL I BACKGROUND OF THEINVENTION this type, and assuming a particular cutting speed, the

maximum feeding speed is depending on two factors, namely firstly thedepth of the cut possible for a particular workpiece and tool, andsecondly the filling capacity of the notches between the teeth of thesawblade. For example, if the length of the cut material engaged by thesawteeth is short when working a comparatively. thin material, thefeeding speed can be increased until the maximum permissible depth ofcut and maximum thickness of the cut chip are obtained, while for anincreased length of the cut in the material,

the limited filling volume of the notches between the teeth is ofgreater importance,and finally necessitates a reduction of the thicknessof the chip by reducing the feeding speed.

In known sawing machines, a certain adaptation to these circumstancestakes place automatically due to the fact that the hydraulic feedingmotor of the sawblade has a chamber of constant pressure for advancingthe sawblade, while the other chamber, which is gradually emptied whilethe sawblade is being fed, is connected by a manual throttle to a returnand discharge conduit, so that at an increased engagement length of thesawteeth, the cutting resistance increases, and between the two sides ofthe feeding piston of the hydraulic feeding motor, an increasingpressure differential is built up due to the fact that the pressuremedium can flow out faster through the throttle than the feeding pistoncan follow. When then the engaged length of the tooth is reduced, anincrease of the feeding speed, and a corresponding increase of thethickness of the cut chip takes place. This automatic regulation is notvery sensitive, and rather slow, and does not permit a real adaptationof the machine to the maximum possible feeding speed at any moment ofthe sawing operation.

SUMMARY OF THE INVENTION above-explained disadvantages are eliminated.

Another object of the invention is to control the feeding of a tool,such as a saw blade, in such a manner that the sawblade operates at anytime with the maximum possible feeding speed, even if the cutcross-sections considerably vary as the saw blade is fed into thematerial.

In order to obtain a reduction of the feeding speed when the load torqueis great, and an increase of the feeding speed when the load torque issmall, the load torque is sensed, for example by an amperemeter in thecircuit of an electric motor driving the saw blade, and a regulatingmember cooperates with first and second stops which are manually set tomaximum and minimum feeding speeds desired in accordance with the cutcross-section of the workpiece.

When the maximum permissible load torque is exceeded, the regulatingmember moves rapidly into engagement with the stop for the minimumfeeding speed,

and then slowly moves toward the stop'for the maximum feeding speed.

The amperemeter sensing the torque acting on the drive motor ispreferably provided with maximum and minimum limit mark members whichlimit the movement of the indicating pointer which controls, preferablythrough an electric circuit, the electromagnetic control means of theregulating throttle. In sawing 0 machines, which are designed forseveral cutting speeds, it is advantageous to automatically change themaximum limit of the sensing indicating pointer when the cutting speedis changed, while the torque is main? tained constant, which may beeffected by exchanging the transformer of the load responsive sensingamperemeter. When several transformers are suitably constructed andarranged, a switching of the cutting speed obtains automatically andsimultaneously the conditions of the torque sensing amperemeter requiredforthe operation of the apparatus.

The invention makes use of the fact that the torque of the drive motoris proportional to the load acting on the sawblade, and the feedingspeed of the sawblade is regulated in such a manner, that the maximumpermissible load for the respective workpiece is not exceeded wherebydamage to the saw blade is prevented. 0n the other hand, the apparatusof the invention assures that most of the cutting is'carried out" in therange of the maximum permissible load, and also with the maximumpossible feeding speed, so that the machine operates at optimalefficiency.

The ampereme ter which senses the load torque acting on the drive motor,may be connected by a pulse, generator to the'control means of theregulating throttle. However, it is preferred to use a relay circuit forthis purpose.

One embodiment of the invention comprises an electric drive motor forrotating a saw blade; feeding means preferably including a hydraulicpiston and cylinder motor for feeding the saw blade into a material;regulating means, preferably including an adjustable throttle connectedwith the hydraulic cylinder and piston motor, and including a movableregulating member; control means including another hydraulic motor, anda reversible electromagnetically controlled valve, connected with theregulating throttle and having a normal position for operating theregulating throttle to slowly increase the feeding speed, and a controlposition, in which the valve is reversed, for operating the regulatingthrottle to rapidly reduce the feeding speed; torque responsivesensi'ngmeans, preferably an amperemeter,

, for sensing the load torque acting on the electric drive motor, andconnected, preferably by a relay circuit, with the electromagnetic meansby which the reversing valve is operated for setting the same to thecontrol position when sensing a maximum load torque so that theregulating throttle rapidly reduces the feeding speed and thereby theload torque until the sensing amperemeter sets, at a minimum loadtorque, the control means back to the normal position; and first andsecond manually settable stops for limiting the movement of theregulating member independently of the control means and sensing meansin two positions in which the regulating throttle sets the feeding meansto a maximal feeding speed and to a minimal feeding speed, respectively,selected for a specific workpiece BRIEF DESCRIPTION OF THE DRAWING FIG.1 is a side view illustrating a rotary sawing machine in a somewhatsimplified manner; FIG. 2 is a schematic and diagrammatic viewillustrating an embodiment of the invention for controlling the sawingmachine shown in FIG. 1;

FIG. 3 is a front viewand FIG. '4 is a side view illustrating a devicefor manually setting'stops for limiting the movement of the speedregulating means of the machine;

FIG. 5a is a schematic view illustrating the sawblade in successivepositions during cutting of a workpiece;

FIG. 5 is a diagram illustrating the variation of the feeding speedduring the' successive cutting of portions of the workpiece as shown inFIG. 5a; and

FIG. 6 is a schematic and diagrammatic view showing particularly theelectric circuit for operating elec- 'tr'omagnetic means for varying thefeeding speed depending on the indications of a load responsiveamperemeter in the circuit of the electric drive motor.

Referring first to FIG. 1, a cold saw has a supporting base 1 providedwith a hinge 2 which an arm 3 is mounted for angular movement. A rotarysaw blade 4 is mounted on the arm, and is driven by a motor 5. A

, workpiece 6 is held by a clampingmeans 7 and 8 on the supporting baseI. An amperemeter 38 is mounted on "farm 3 and connected into thecircuit of the electric motor 5 to indicate the current flowing throughmotor 5, which is proportionate to the load torque exerted by the sawblade 4 on motor 5 during cutting of the workpiece 6.

The tilting of arm 3 with sawblade 4 to move the same relative to theworkpiece 6, is effected by a cylinder and piston hydraulic motorarranged in a housing part 12 which is turnable about a shaft 10 andincludes a feeding cylinder 9 in which a feeding piston 22 is mountedwhose position rod 11 is pivotally connected with the arm -3. Housingpart 12 may also cover control means and regulating means for thefeeding piston 22, which will be explained with reference to FIG. 2.

Feeding cylinder 9' and feeding piston 22 are also shown in FIG. 2,audit will be seen that piston 22 forms chambers 13 and 18 in cylinder9. A pump 14 pumps an operating liquid from a reservoir 27 through asuction conduit-28 into a pressure conduit 26 in which-a pressurelimiting valve-1'5 'isprovided. When the per"- missiblepressure set 'bylimit valve 15 is exceeded,

pressure liquid is discharged through return conduits 16, 17 intoreservoir 27, so that the pressure in conduit 16 is lower than thepressure in conduit 26. A return conduit 19 connects chamber 18 withregulating throttle which discharges through return conduit 17. The 5reversing valve 23 has two positions, and has a normal position, shownin FIG. 2 for connecting chamber 13 with pressure conduit 26, and areversed position connecting chamber 18 through a conduit withregulating throttle 20 and return conduit 17. An electromagnetic means Mcontrols reversing valve 23.

4 The combined effect of the pressure in cylinder chamber 13 and of thecutting resistance exerted on the sawblade 4, moves feeding piston 22 toreduce the volume of chamber 18 so that pressure fluid flows throughconduit 19 and regulating throttle 20 into the return conduit 17. Theregulating member 21, which is connected with regulating throttle 20,determinesthe speed of movement of piston 22 and thereby the feedingspeed of sawblade 4.

When a sawing operation has been completed, the feeding piston. 22 canbe moved in the opposite direction for lifting the sawblade 4 out of theworkpiece 6, by reversing the magnetically operated valve 23 so that thechamber 13 is connected by conduit 24 to the return conduit 17, whilechamber 18 is connected by conduit 25 to the pressure conduit 26 of pump14.

The regulating member21 by which regulating throttle 20 is adjusted, isconnected by an adjustable slip clutch 29 with control means operatedunder control of the amperemeter 28 which constitutes a torqueresponsive sensing means sensing the load torque acting on the drivemotor 5.

The control means include a hydraulic control motor 32 including acontrol cylinder and a control piston connected by a piston rod 31 andlever (FIG. 3) with the slip clutch 20. A reversing control valve 34 isoperated by electromagnetic means 34a under the control of amperemeter28, which will explained with reference to FIG. 6. A conduit 35 passesthrough control valve 34 into the chamber 33 of the cylinder and pistonmeans 32, while a conduit 39, connected with I the return conduit 17,passes through control valve 34 and into the other control chamber 36through a check valve and an adjustable throttle 37.

In the position of the control means 32, 40, 37, 34 shown in FIG. 2,pressure medium in conduit 35 operates piston and piston rod 31 to turnregulating member 21 in one direction at a slow speed due to the factthat check valve 40 is closed, and throttle 37 restricts the flow out ofcontrol chamber 36. When reversing control valve 34 is shifted to acontrol position, the flow is reversed, and pressure fluid is suppliedthrough check valve 40 into chamber 36, while fluid in chamber 33 isdischarged through conduit 35 and conduit 39 into the reservoir 2, andsince no throttle is provided in this path of flow, the adjustment ofthe regulating throttle 21 to a wider open condition, and thereby anincrease of the feeding speed of the sawblade 4 is obtained quickly.

The electromagnetic means 34a of the control valve 34 is controlled bytorque responsive sensing means, schematically shown in FIG. 2 to be theamperemeter 38 of the electric drive motor 5, see also FIG. 1.

The amperemeter 38 may operate a pulse generator, not shown, for theelectromagnetically controlled valve 34. The sensing means 38 is set tothe maximal load of the sawblade 4, and to the corresponding load ofmotor 5 in such a manner that the control valve 34 is shifted from theillustrated normal position by the pulse generator, not shown, to thecontrol position when the set maximum load of drive motor 5 is exceeded,and sensed by sensing means 38. Consequently, at a selected maximum loadand load torque, the hydraulic motor 32 rapidly operates the regulatingmember 21 to reduce the cross section of the regulating throttle 20, sothat the feeding speed of the saw blade 4 is reduced. Due to thereduction of the feeding speed of saw blade 4, the load torque of motor5 is immediately reduced, so that control valve 34 is shifted under thecontrol of the load torque responsive means 38 and the pulse generator,not shown, to the initial position so that regulating member 21 isoperated by the hydraulic control piston cylinder means 32 to adjust theregulating throttle to a higher feeding speed, the adjustment being slowdue to the effect of throttle 37.

As shown in FIGS. 3 and 4, two manually settable stops 41 and 42 areprovided which limit the range of adjustment of regulating member 21,and thereby of the regulating throttle to predetermined maximum andminimum feeding speeds. Regulating member 21 has a projecting nose 43which cooperates in the illustrated normal position of the handle 44with the settable stops 41 and 42. When regulating member 21 is turnedto a position abutting stop 4l"or to a position abutting stop 42 by thecontrol piston and cylinder means 32, the piston and piston rod 31 maycontinue its movement due to the provision of a slip clutch 29 betweenthe piston rod 31 and its connecting link 30 and the regulating member21.

The use of the stops 41 and 42 has the advantage that the regulatingmember 21 can be automatically moved only between two position,associated with maximum and minimum feeding speed of the saw blade 4,while farther movements of regulating member 21 and unnecessaryadjustment times are eliminated.

In certain cases it may be advantageous to set the regulating member 21manually by handle 44 to angular positions beyond the limits provided bystops 41 and 42. Handle 44 is then pressed down against the action ofthe spring 45 so that nose 43 is raised to a position passing over theset stops 41 and 42. In the normal position of FIG. 4, nose 43 movesalong a circular path in which the stops 41 and 42 are located.

The above-described embodiment of the invention is particularly suitablewhen the sawing machine is provided with a hydraulic feeding means forthe sawblade, so that pressure fluid is available. For sawing machinesin which the feeding movement of the sawblade is not obtained by ahydraulic motor, it may be advantageous to connect the torque responsivesensing means 38 with the regulating member 21 by an electric steppingmotor, not shown.

FIG. 6 illustrates a preferred electric circuit for connecting thetorque responsive amperemeter 38 with the electromagnetic operatingmeans 34a of the reversing control valve 34.

The electric drive motor 5- is a three-phase motor connected to threelines 74a, 74b, 740. In the line 740, three different transformers 57,58 and 59 are connected, each of which has two windings so that eachwinding induces a corresponding current in the other winding. The threetransformers 37, 38, and 39 are selected for setting three differentrotary speeds of motor 5, and three different cutting speeds of thesawblade 4. The three different cutting speeds are diagrammaticallyindicated at I, II and III in FIG. 6.

A switching means 60 is connected with the transformers 57, 58, 59, andwith the amperemeter 38, so that the latter can be connected byoperation of the manual member 61 to anyone of the three transformers57, 58, 59. The change of the rotary speed of the sawblade 4 can beeffected electrically or by means of a motor. In a sawing machine ofthis type whichhas several cutting speeds, it is possible to obtainautomatically, upon shifting to another cutting speed, a variation ofthe respective value sensed by sensing means 38 at the same torque,which is accomplished by selecting one of the transformers 37, 38, 39for connection with the sensing amperemeter 38.

As shown in FIG. 6, the amperemeter 38 has a movable indicator pointer62 which indicates the load acting on motor 5. By the three transformers57, 58, 59, the currents occurring at three different speeds andindicated by amperemeter 38, are varied in such a.

manner that the indicating pointer 62 indicates the torque of thesawblade directly at a corresponding graduated scale 62d.

A maximum limit marking member 66 can set by means of a hand wheel 67 onamperemeter 38. When the indicator member 62 reaches this limit markingmember 66, the relay 69 is actuated so that the relay 71 isenergized andcloses contact 71/2 so that electromagnetic means 34a operates thereversing control valve 34 so that the pressure liquid can flow throughthe check valve 40 into cylinder chamber 36, and effect fast closing ofthe regulating throttle 20. In this manner, the feeding speed of the sawblade is quickly reduced so that indicator pointer 62 is moved toindicate the corresponding reduced load of motor 5.

When the other limit marking member 64, set by the handwheel 65, isreached by the indicator pointer 38, relay 68 is actuated, so that itscontact energizes relay 71 again whereby the electromagnetic means 34aof the reversing control valve 34 is shifted. This has the effeet thatthe control means 32, 34 slowly open the regulating throttle 20 so thatthe feeding speed of the saw blade is slowly increased until indicatorpointer 62 reaches the maximum limit marking member 66 again.

It should be noted that the manually operated switch 70 can be operatedto eliminate the above-described automatic regulation of the feedingspeed by amperemeter 38, if operational conditions make this advisable.The contacts 71/1 and 71/2 of relay 71 are actually located within thehousing of the relay 71.

While the indicator pointer 62 may be mechanically cooperate with limitmarking members 66 and 64, it is possible to obtain the requiredelectrical control signals by an inductive connection between the limitmarking members 64 and 66 and the indicator pointer 62. For example,members 64 and 66 may be provided with windings producing a magneticfield which is disturbed by indicator pointer 66 when moving into closeproxi'mity with members 64 or 66, which may be U-shaped to increase theforce of the respective magnetic field. Instead of mechanical contactbetween indicator pointer 62 and the limit marking members 64 and 66, a

light barrier and photocells may be used.

In the circuit illustrated in FIG. 6 a circuit part to which indicatorpointer 62 and limit marking members 64, 66 are connected, has conductorbars connected I the regulating means 21, are operated by the controlmeans 32, 34 to effect a slow increase of the feeding speed, as long asthe maximum permissible load torque has not been reached at the drivemotor 5. When this condition is sensed by the amperemeter 38, controlpiston means 31 presses the operating liquid out of control chamber 36and through throttle 37, so that it is possible to adjust the speed ofthis movement by adjust- .ing throttle 37. When a feeding speed isreached at which the saw blade 4 produces the maximum permissible load,the control means 32, 34 are shifted so that control piston 31 movesrapidly while reducing the volume of pressure chamber 33 through thefree return conduit 35, in which no throttle is provided. As a result,the load on the saw blade 4 is reduced, which causes a shifting ofcontrol valve 34 and again a gradual increase of the feeding speed ofthe saw blade.

The apparatus of the invention is very sensitive, so that control piston31 performs only very small movements substantially in the range of themaximum feeding' speed.

The regulating member 21 can be provided with a graduated scale, shownin FIG. 3, for indicating the feeding speed of the sawing blade.

Irrespective of the function of the torque responsive amperemeter 38,the manually settable stops 41 and 42 limit the feeding speed which canvary only between a maximum feeding speed and a minimum feeding speed,determined'by manually setting the stops 41 and 42. By the provision ofa minimum feeding speed stop, the feeding speed cannot be rapidlyreduced to a lower value than is necessary.

FIGS. Send 5 show diagrammatically an operation of the saw blade underthe control of the apparatus of the invention. In FIG. 5a, the sawblade4 is shown in several positions 51 to 56 assumed while being fed byfeeding means 22, 11. A I-profile is being cut. As shown in FIG. 5a, inthe position 51 of saw blade 4, the length of the cut surface engaged bythe teeth of the saw blade is very small, so that it is possible tooperate at a maximum feeding speed and with a maximum depth of cut andthickness of the chips. In the position 52, the sawblade' engages theweb of the bar 59 so that the load torque acting on the sawblade driveis rapidly increased until the set maximum value is reached. In themanner described with reference to FIG. 2, the feeding speed is Irapidly reduced and then slowly rises as indicated at 53 in FIG. 5 untilthe set maximum speed is obtained, which causes again a reduction of thefeeding speed.

The same adjustments are obtained when the sawing blade 4 is in theposition 54, while in the position 55 in which the sawblade teeth moveout of the web of bar 59, see FIG. 5a, a higher feeding speed ispossible which is then once reduced. In the meantime, the sawbladearrives in the position 56, so that the feeding speed can rise to themaximum speed at which the operation was started in the position 51 ofthe sawblade 4 It will be understood that each of the elements describedabove, or two or more together, may also find a useful application inother types of feed control apparatus for rotary tools differing fromthe types described above.

While the invention has been illustrated and described as embodied in afeeding speed control apparatus for a rotary saw blade having manuallysettable means for limiting the feeding speed between a maximum and aminimum desired for a workpiece, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

I claim:

1. Feed control apparatus for a rotary tool, comprising a motor meansfor rotating the tool; feeding means for feeding the tool into amaterial; regulating means connected with said feeding means forcontrolling the feeding speed of said tool and including a movableregulating member; control means connected with said regulating meansand having a normal position for operating said regulating means toslowly increase the feeding speed, and a control position for operatingsaid regulating means to rapidly reduce the feeding speed; torqueresponsive sensing means for sensing the load torque acting on saidmotor means and connected with said control means for setting the sameto said control position when sensing a maximum load torque so that saidregulating means rapidly reduces the feeding speed and thereby said loadtorque until said sensing means sets at a minimum load torque saidcontrol means back to said normal position; and first and secondmanually settable stops for limiting movement of said regulating memberindependently of said control means and sensing means in two positionsin which said regulating means sets said feeding means to a maximumfeeding speed and to a minimum feeding speed, respectively, selected fora specific workpiece by setting said stops, so that said regulatingmember moves rapidly toward said second stop for obtaining minimumfeeding speed and slowly toward said first stop for obtaining maximumfeeding speed. I

2. Feed control apparatus as claimed in claim 1 wherein said controlmeans include a movable control member operated under the control ofsaid torque responsive sensing means; and means including a slip clutchconnecting said control member with said regulating member so that saidcontrol member can continue to move under the control of said sensingmeans when said regulating member abuts one of said settable stops.

3. Feed control apparatus as claimed in claim 1 wherein said controlmeans include a control cylinder and a control piston forming in saidcontrol cylinder first and second control chambers, pump means includinga pressure conduit and a return conduit, a reversing control valvehaving a normal position for connecting said pressure conduit with saidfirst control chamber and said return conduit with said second controlchamber and a control position reversing the flow, a throttle connectingsaid second control chamber with said reversing control valve, a checkvalve connecting said reversing valve with said second control chamber,operating means controlled by said torque responsive means for shiftingsaid reversing control valve to said control position when sensing amaximum load torque acting on said motor means; and means connectingsaid control piston with said regulating member.

4. Feed control apparatus as claimed in claim 1 comprising manuallyoperated means connected to said regulating member for operating saidregulating means to set said feeding means to different feeding speeds.

5. Feed control apparatus as claimed in claim 4 wherein said manuallyoperated means has a normal position moving along a path limited by saidsettable stops, and a displaced position moving along a different pathpassing over said settable stops for controlling said regulating meansand feeding means to obtain feeding speeds exceeding said maximum andminimum feeding speeds.

6. Feed control apparatus as claimed in claim 1 wherein said feedingmeans includes a feeding cylinder and a feeding piston forming feedingchambers in said feeding cylinder, said feeding piston being connectedwith said tool, pump means including a pressure conduit and a returnconduit, and reversing valve means for connecting said conduits withsaid feeding chambers, respectively; and wherein said regulating meansincludes adjustable throttle means operated by said control means andbeing located in said return conduit for reducing flow out of saidfeeding cylinder during feeding movement of the tool.

7. Feed control apparatus as claimed in claim 1 wherein said torqueresponsive sensing means includes at least one limit mark membersettable to a selected maximum load torque, a movable member cooperatingwith said limit member and being responsive to the load torque, andmeans for connecting said movable member with said control means so thatthe feeding speed is rapidly reduced when said movable member reachessaid limit mark member.

8. Feed control apparatus as claimed in claim 7 wherein said torqueresponsive sensing means include a second limit mark member settable toa selected minimum load torque so that the feedingspeed is slowlyincreased by said control means when said movable member reaches saidsecond limit mark member.

9. eed control apparatus as claimed ll'l claim 8 wherein said motormeans includes an electric motor; and wherein said torque responsivesensing means includes an amperemeter having said movable member as anindicator; wherein said operating means include electromagnetic means;and circuit means connecting said limit mark members and said indicatorwith said electromagnetic means.

10. Feed control apparatus as claimed in claim 1 wherein said controlmeans include a control cylinder and a control piston forming in saidcontrol cylinder first and second control chambers, pump means includinga pressure conduit and a return conduit, a reversing control valvehaving a normal position for connecting said pressure conduit with saidfirst control chamber and said return conduit with said second controlchamber and a control position reversing the flow, a throttle connectingsaid second control chamber with said reversing control valve, a checkvalve connecting said reversing valve with said second control chamber,operating means controlled by said torque responsive means for shiftingsaid reversing control valve to said control position when sensing amaximum load torque acting on said motor means; and means connectingsaid control piston with said regulating member; wherein said feedingmeans includes a feeding cylinder and a feeding piston forming feedingchambers in said feeding cylinder, said feeding piston being connectedwith said tool, pump means including a pressure conduit and a returnconduit, and reversing valve means for connecting said conduits withsaid feeding chambers, respectively; wherein said regulating meansincludes adjustable throttle means operated by said control means andbeing located in said return conduit for reducing flow out of saidfeeding cylinder during feeding movement of the tool; wherein said motormeans includes an electric motor; wherein said torque responsive sensingmeans includes an amperemeter having said movable member as anindicator; wherein said operating means include electromagnetic means;and circuit means connecting said limit mark members and said indicatorwith said electromagnetic means.

1. Feed control apparatus for a rotary tool, comprising a motor meansfor rotating the tool; feeding means for feeding the tool into amaterial; regulating means connected with said feeding means forcontrolling the feeding speed of said tool and including a movableregulating member; control means connected with said regulating meansand having a normal position for operating said regulating means toslowly increase the feeding speed, and a control position for operatingsaid regulating means to rapidly reduce the feeding speed; torqueresponsive sensing means for sensing the load torque acting on saidmotor means and connected with said control means for setting the sameto said control position when sensing a maximum load torque so that saidregulating means rapidly reduces the feeding speed and thereby said loadtorque until said sensing means sets at a minimum load torque saidcontrol means back to said normal position; and first and secondmanually settable stops for limiting movement of said regulating memberindependently of said control means and sensing means in two positionsin which said regulating means sets said feeding means to a maximumfeeding speed and to a minimum feeding speed, respectively, selected fora specific workpiece by setting said stops, so that said regulatingmember moves rapidly toward said second stop for obtaining minimumfeeding speed and slowly toward said first stop for obtaining maximumfeeding speed.
 1. Feed control apparatus for a rotary tool, comprising amotor means for rotating the tool; feeding means for feeding the toolinto a material; regulating means connected with said feeding means forcontrolling the feeding speed of said tool and including a movableregulating member; control means connected with said regulating meansand having a normal position for operating said regulating means toslowly increase the feeding speed, and a control position for operatingsaid regulating means to rapidly reduce the feeding speed; torqueresponsive sensing means for sensing the load torque acting on saidmotor means and connected with said control means for setting the sameto said control position when sensing a maximum load torque so that saidregulating means rapidly reduces the feeding speed and thereby said loadtorque until said sensing means sets at a minimum load torque saidcontrol means back to said normal position; and first and secondmanually settable stops for limiting movement of said regulating memberindependently of said control means and sensing means in two positionsin which said regulating means sets said feeding means to a maximumfeeding speed and to a minimum feeding speed, respectively, selected fora specific workpiece by setting said stops, so that said regulatingmember moves rapidly toward said second stop for obtaining minimumfeeding speed and slowly toward said first stop for obtaining maximumfeeding speed.
 2. Feed control apparatus as claimed in claim 1 whereinsaid control means include a movable control member operated under thecontrol of said torque responsive sensing means; and means including aslip clutch connecting said control member with said regulating memberso that said control member can continue to move under the control ofsaid sensing means when said regulating member abuts one of saidsettable stops.
 3. Feed control apparatus as claimed in claim 1 whereinsaid control means include a control cylinder and a control pistonforming in said conTrol cylinder first and second control chambers, pumpmeans including a pressure conduit and a return conduit, a reversingcontrol valve having a normal position for connecting said pressureconduit with said first control chamber and said return conduit withsaid second control chamber and a control position reversing the flow, athrottle connecting said second control chamber with said reversingcontrol valve, a check valve connecting said reversing valve with saidsecond control chamber, operating means controlled by said torqueresponsive means for shifting said reversing control valve to saidcontrol position when sensing a maximum load torque acting on said motormeans; and means connecting said control piston with said regulatingmember.
 4. Feed control apparatus as claimed in claim 1 comprisingmanually operated means connected to said regulating member foroperating said regulating means to set said feeding means to differentfeeding speeds.
 5. Feed control apparatus as claimed in claim 4 whereinsaid manually operated means has a normal position moving along a pathlimited by said settable stops, and a displaced position moving along adifferent path passing over said settable stops for controlling saidregulating means and feeding means to obtain feeding speeds exceedingsaid maximum and minimum feeding speeds.
 6. Feed control apparatus asclaimed in claim 1 wherein said feeding means includes a feedingcylinder and a feeding piston forming feeding chambers in said feedingcylinder, said feeding piston being connected with said tool, pump meansincluding a pressure conduit and a return conduit, and reversing valvemeans for connecting said conduits with said feeding chambers,respectively; and wherein said regulating means includes adjustablethrottle means operated by said control means and being located in saidreturn conduit for reducing flow out of said feeding cylinder duringfeeding movement of the tool.
 7. Feed control apparatus as claimed inclaim 1 wherein said torque responsive sensing means includes at leastone limit mark member settable to a selected maximum load torque, amovable member cooperating with said limit member and being responsiveto the load torque, and means for connecting said movable member withsaid control means so that the feeding speed is rapidly reduced whensaid movable member reaches said limit mark member.
 8. Feed controlapparatus as claimed in claim 7 wherein said torque responsive sensingmeans include a second limit mark member settable to a selected minimumload torque so that the feeding speed is slowly increased by saidcontrol means when said movable member reaches said second limit markmember.
 9. Feed control apparatus as claimed in claim 8 wherein saidmotor means includes an electric motor; and wherein said torqueresponsive sensing means includes an amperemeter having said movablemember as an indicator; wherein said operating means includeelectromagnetic means; and circuit means connecting said limit markmembers and said indicator with said electromagnetic means.